package cn.iocoder.yudao.module.wine.utils;

/**
 * 雪花算法生成订单号
 * @author zyc
 * @createDate 2024/5/9 17:13
 */
public class SnowflakeIdGeneratorUtil {
    // 起始的时间戳
    private final static long START_TIMESTAMP = 1715246219000L; // 2024-05-09

    // 每一部分占用的位数
    private final static long SEQUENCE_BIT = 12; // 序列号占用的位数
    private final static long MACHINE_BIT = 5;   // 机器标识占用的位数
    private final static long DATACENTER_BIT = 5; // 数据中心占用的位数

    // 每一部分的最大值
    private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);
    private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
    private final static long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_BIT);

    // 每一部分向左的位移
    private final static long MACHINE_LEFT = SEQUENCE_BIT;
    private final static long DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
    private final static long TIMESTAMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;

    private static long datacenterId = 1;  // 数据中心
    private static long machineId = 1;     // 机器标识
    private static long sequence = 0L; // 序列号
    private static long lastTimestamp = -1L; // 上一次时间戳

    public SnowflakeIdGeneratorUtil() {
        if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
            throw new IllegalArgumentException("Datacenter ID can't be greater than " + MAX_DATACENTER_NUM + " or less than 0");
        }
        if (machineId > MAX_MACHINE_NUM || machineId < 0) {
            throw new IllegalArgumentException("Machine ID can't be greater than " + MAX_MACHINE_NUM + " or less than 0");
        }
        this.datacenterId = datacenterId;
        this.machineId = machineId;
    }

    public static synchronized String generateId() {
        long timestamp = System.currentTimeMillis();
        if (timestamp < lastTimestamp) {
            throw new RuntimeException("Clock moved backwards. Refusing to generate id.");
        }

        if (timestamp == lastTimestamp) {
            sequence = (sequence + 1) & MAX_SEQUENCE;
            if (sequence == 0) {
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0L;
        }

        lastTimestamp = timestamp;
        long no = ((timestamp - START_TIMESTAMP) << TIMESTAMP_LEFT) |
                (datacenterId << DATACENTER_LEFT) |
                (machineId << MACHINE_LEFT) |
                sequence;
        return String.valueOf(no);
    }


    public static synchronized Long generateLongId() {
        long timestamp = System.currentTimeMillis();
        if (timestamp < lastTimestamp) {
            throw new RuntimeException("Clock moved backwards. Refusing to generate id.");
        }

        if (timestamp == lastTimestamp) {
            sequence = (sequence + 1) & MAX_SEQUENCE;
            if (sequence == 0) {
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0L;
        }

        lastTimestamp = timestamp;
        long no = ((timestamp - START_TIMESTAMP) << TIMESTAMP_LEFT) |
                (datacenterId << DATACENTER_LEFT) |
                (machineId << MACHINE_LEFT) |
                sequence;
        return no;
    }

    private static long tilNextMillis(long lastTimestamp) {
        long timestamp = System.currentTimeMillis();
        while (timestamp <= lastTimestamp) {
            timestamp = System.currentTimeMillis();
        }
        return timestamp;
    }
}
